The millimeter- and submillimeter-wave spectra of PtCO in the ground and v(2) excited vibrational states were observed by employing a source-modulated microwave spectrometer. The PtCO molecule was generated in a free space cell by the sputtering reaction from a platinum sheet lining the inner surface of a stainless steel cathode using a dc glow plasma of CO and Ar. From the molecular constants determined for the v(2) excited state, especially the /-type doubling constant, its harmonic wavenumber was determined to be approximate to420 cm(-1), which resolved the reported discrepancy between the previous matrix-infrared and theoretical estimates. (C) 2004 Elsevier B.V. All rights reserved.